This invention generally relates to the rolling of metal ingots into sheet and plate products and in particular to an improved liquid application device or spray bar for the application of lubricants or coolants onto the surfaces of the workpiece or the work rolls or the backup rolls of a rolling mill, during the rolling process.
In the rolling of metal products, lubricants or coolants (hereinafter "liquids"), are applied to the workpiece or the work rolls or the backup rolls, or all three, to control both the temperatures and the frictional properties of these surfaces. Usually, such liquids are applied at both the entry and exit sides of the rolling mill stand.
In commercial rolling mills the amount of liquid applied and the pattern of liquid distribution on the work rolls are controlled to obtain the thermal gradients which will ensure that the proper crown will be maintained on the work rolls. Without such temperature control, undesirable thermal gradients build up along the length of the roll causing differential thermal expansion which distorts the crown of the roll and which results in differential thickness reductions and tension differences across the width of the workpiece, i.e. unflat sheet or plate.
For most commercial rolling, liquids are directly applied to both the work rolls and backup rolls through a series of nozzles or clusters of nozzles disposed along the length of the rolls, and each of the nozzles or clusters of nozzles are supplied with liquid from a separate liquid source which has independently controlled valving means in order to provide the desired liquid distribution on the rolls.
Because of the harsh environment in which these spray devices are used, frequent malfunctions occur causing mill shutdowns or ineffective cooling of the workpiece, the work rolls or the backup rolls which often result in unflat products. The individual valving means can plug up due to the buildup or accumulation of particulate and other debris which frequently accompany the liquids, in which case little or no liquid passes through to an area of the work rolls which expands due to heat buildup. On the other hand the valving means can stick open in which case unwanted liquid flow continues to a particular area of the workpiece or rolls causing undesirable cooling. Generally, when the control valves are maintained in the area of the rolls and workpiece they are exposed to a very high probability of damage. The valving arrangement can be removed to a much safer location away from the rolling mill where the chances for damage can be significantly reduced, but this does not avoid having liquid sources and individual valving means for each particular nozzle or cluster of nozzles.
Ideally, commercial spray devices should be durable and have the flexibility to make changes in coolant or lubricant application which are required by changes in the rolling conditions or workpiece characteristics. As an example of the latter characteristic, in the operation of most rolling mills the workpieces have widely varying widths and in such cases the coolant spray to the work rolls must be controlled to the edge of the workpiece. Coolant on the work rolls beyond the edge of the workpiece is undesirable and should be terminated. Additionally, although there are usually other strip flatness control means provided in a rolling mill, control of the liquid distribution over the work rolls and backup rolls is often necessary to correct for or to minimize center buckles, quarter buckles and edge waviness in the workpiece. There have been prior spray devices which allow for a significant number of such changes in coolant or lubricant distribution across the rolls but they have usually not been very durable.
Examples of prior art devices are found in the following references:
______________________________________ US 804,807 US 3,941,611 US 3,237,872 US 4,081,141 US 3,574,338 US 4,247,067 US 3,771,730 US 4,312,377 US 3,880,358 ______________________________________
It is against this background that the present invention was developed.